Electrolytic processing apparatus and method

ABSTRACT

There is provided an electrolytic processing apparatus and method that can effect processing of a workpiece with high processing precision and can produce an intended form of processed workpiece with high accuracy of form. The electrolytic processing apparatus includes: a processing electrode which can come close to a workpiece; a feeding electrode for feeding electricity to the workpiece; an ion exchanger disposed in at least one of the space between the workpiece and the processing electrode and the space between the workpiece and the feeding electrode; a fluid supply section for supplying a fluid to the space between the workpiece and at least one of the processing electrode and the feeding electrode; and a power source for supplying an electric power between the processing electrode and the feeding electrode while arbitrarily controlling at least one of a voltage and an electric current.

TECHNICAL FIELD

This invention relates to an electrolytic processing apparatus andmethod, and more particularly to an electrolytic processing apparatusand method useful for processing a conductive material present in thesurface of a substrate, especially a semiconductor wafer, or forremoving impurities adhering to the surface of a substrate.

BACKGROUND ART

In recent years, instead of using aluminum or aluminum alloys as amaterial for forming interconnection circuits on a substrate such as asemiconductor wafer, there is an eminent movement towards using copper(Cu) which has a low electric resistivity and high electromigrationresistance. Copper interconnects are generally formed by filling copperinto fine recesses formed in the surface of a substrate. There are knownvarious techniques for forming such copper interconnects, including CVD,sputtering, and plating. According to any such technique, a copper filmis formed in the substantially entire surface of a substrate, followedby removal of unnecessary copper by chemical mechanical polishing (CMP).

FIGS. 1A through 1C illustrate, in sequence of process steps, an exampleof forming such a substrate W having copper interconnects. As shown inFIG. 1A, an insulating film 2, such as an oxide film of SiO₂ or a filmof low-k material, is deposited on a conductive layer la in whichsemiconductor devices are formed, which is formed on a semiconductorbase 1. A contact hole 3 and a trench 4 for interconnects are formed inthe insulating film 2 by the lithography/etching technique. Thereafter,a barrier layer 5 of TaN or the like is formed on the entire surface,and a seed layer 7 as an electric supply layer for electroplating isformed on the barrier layer 5.

Then, as shown in FIG. 1B, copper plating is performed onto the surfaceof the substrate W to fill the contact hole 3 and the trench 4 withcopper and, at the same time, deposit a copper film 6 on the insulatingfilm 2. Thereafter, the copper film 6 and the barrier layer 5 on theinsulating film 2 are removed by chemical mechanical polishing (CMP) soas to make the surface of the copper film 6 filled in the contact hole 3and the trench 4 for interconnects and the surface of the insulatingfilm 2 lie substantially on the same plane. An interconnection composedof the copper film 6 as shown in FIG. 1C is thus formed.

Components in various types of equipments have recently become finer andhave required higher accuracy. As sub-micro manufacturing technology hascommonly been used, the properties of materials are largely influencedby the processing method. Under these circumstances, in such aconventional machining method that a desired portion in a workpiece isphysically destroyed and removed from the surface thereof by a tool, alarge number of defects may be produced to deteriorate the properties ofthe workpiece. Therefore, it becomes important to perform processingwithout deteriorating the properties of the materials.

Some processing methods, such as chemical polishing, electrolyticprocessing, and electrolytic polishing, have been developed in order tosolve this problem. In contrast with the conventional physicalprocessing, these methods perform removal processing or the like throughchemical dissolution reaction. Therefore, these methods do not sufferfrom defects, such as formation of an altered layer and dislocation, dueto plastic deformation, so that processing can be performed withoutdeteriorating the properties of the materials.

A processing method, which makes use of a catalytic reaction of the ionexchanger and carries out processing in ultrapure water, has beendeveloped as electrolytic processing. FIG. 2 illustrates the principleof this electrolytic processing. FIG. 2 shows the ionic state when anion exchanger 12 a mounted on a processing electrode 14 and an ionexchanger 12 b mounted on a feeding electrode 16 are brought intocontact with or close to a surface of a workpiece 10, while a voltage isapplied via a power source 17 between the processing electrode 14 andthe feeding electrode 16, and a liquid 18, e.g. ultrapure water, issupplied from a liquid supply section 19 between the processingelectrode 14, the feeding electrode 16 and the workpiece 10. In the caseof this electrolytic processing, water molecules 20 in the liquid 18such as ultrapure water are dissociated efficiently by using the ionexchangers 12 a, 12 b into hydroxide ions 22 and hydrogen ions 24. Thehydroxide ions 22 thus produced, for example, are carried, by theelectric field between the workpiece 10 and the processing electrode 14and by the flow of the liquid 18, to the surface of the workpiece 10opposite to the processing electrode 14 whereby the density of thehydroxide ions 22 in the vicinity of the workpiece 10 is enhanced, andthe hydroxide ions 22 are reacted with the atoms 10 a of the workpiece10. The reaction product 26 produced by this reaction is dissolved inthe liquid 18, and removed from the workpiece 10 by the flow of theliquid 18 along the surface of the workpiece 10. Removal processing ofthe surface of the workpiece 10 is thus effected.

In carrying out electrolytic processing of a workpiece by disposing anion exchanger between the workpiece and at least one of a processingelectrode and a feeding electrode, as described above, it has generallybeen difficult to control the processing rate and the end point ofprocessing.

When the electrolytic processing is carried out while controlling theelectric current supplied between the processing electrode and thefeeding electrode at a constant value, the processing rate, inprinciple, becomes constant so that the processing area of the workpiecedoes not change, whereby control of the processing rate during theprocessing is made with ease. Moreover, since in this case theintegrated amount of electricity can be calculated with ease, it is easyto determine the processing amount and the end point of processing.

If the processing area changes, however, the processing rate alsochanges. In this regard, as shown in FIGS. 3A through 3D, when a copperfilm 6, embedded in interconnect trenches 4 formed in the surface of asubstrate W, is polished by electrolytic processing under a constantelectric current, a barrier layer 5 composed of an insulator becomesexposed on the surface of the substrate W with the progress ofpolishing. When the barrier layer 5 becomes exposed on the surface ofthe substrate W, the processing area decreases dependent on theline/space ratio and the interconnect pattern density, causing a rapidrise in the processing rate.

Further, when removing an electrically conductive film, such as thecopper film 6, as a to-be-processed material in the surface of asubstrate W, the electric resistance of the conductive film increaseswith a decrease in the film thickness. Accordingly, when electrolyticprocessing is carried out under a controlled constant electric current,the voltage applied between the processing electrode and the feedingelectrode increases with a degree in the film thickness. The rate of theincrease of voltage becomes larger as the processing approaches the endpoint when the interconnect pattern becomes exposed. FIG. 4 shows achange (increase) with time in the voltage applied in electrolyticprocessing as carried out under a controlled constant electric current.As shown in FIG. 4, the larger the current density is, the larger is therate of increase in voltage. The increase in voltage is because theapplied voltage is in inverse proportion to the film thickness of copperfilm. In the case where the voltage rapidly rises, control of the endpoint of processing is effected with difficulty. In addition, anexcessive rise in applied voltage can give rise to dielectric breakdown(so-called discharge) of ultrapure water, causing a physical damage tothe workpiece.

On the other hand, when the electrolytic processing is carried out whilecontrolling the voltage applied between the processing electrode and thefeeding electrode at a constant value, the processing rate decreasesrapidly with a rapid decrease in the processing area. In this regard, asshown in FIGS. 5A through 5D, when a copper film 6, embedded ininterconnect trenches 4 formed in the surface of a substrate W, ispolished by electrolytic processing under a constant voltage, a barrierlayer 5 composed of an insulator becomes exposed on the surface of thesubstrate W with the progress of polishing. When the barrier layer 5 isexposed on the surface of the substrate W, the processing area decreasesand the electric current becomes hard to flow, resulting in a rapiddecrease in the processing rate. Further, a conductive film, such as thecopper film 6, increases its electric resistance with a decrease in thefilm thickness, and the electric current value decrease with theincrease in electric resistance. The degree of the decrease in currentvalue becomes smaller as the processing approaches the end point. FIG. 6shows a change with time in the electric current in electrolyticprocessing as carried out under a controlled constant voltage. A changein the processing rate is therefore small near the end point ofprocessing. Accordingly, as compared to the case of controlling anelectric current at a constant value, it is easier to securely terminatethe processing at the end point.

As described above, however, when carrying out electrolytic processingby supplying a constant voltage between the processing electrode and thefeeding electrode, the electric current changes with time. Theprocessing rate also changes with the change in electric current, makingit difficult to control the processing rate during processing.

Further, with the electrolytic processing of an electrically conductivematerial carried out by using an ion exchanger in the above-describedmanner, it is not possible to directly apply thereto a numerical controlmechanism generally employed in conventional mechanical processing. Inthis regard, an electrolytic processing method utilizes a chemicalinteraction between OH⁻ ions and the atoms of a workpiece. Accordingly,the processing phenomenon occurs even when a workpiece and a tool(electrode) is not in contact with each other. Electrolytic processingis thus differentiated in the processing principle from mechanicalprocessing in which processing is effected by physical destruction of aworkpiece. More specifically, in a common mechanical processing,processing is effected by allowing a workpiece and a tool, which are incontact with each other, to make a relative movement so as to physicallydestruct the workpiece. The progress of processing may be stopped byreleasing the contact between the workpiece and the tool e.g. when anintended processing amount is reached. The processing does not progressany more even when the tool passes over the surface of the workpiece. Onthe other, according to the electrolytic processing method whichutilizes a chemical interaction between the reaction species and aworkpiece, as described above, the processing phenomenon occurs when theamount of the reaction species reaches a certain level, even when thetool (electrode) is not in contact with the workpiece. Accordingly, theprocessing phenomenon inevitably occurs when the tool (electrode) passesover the surface of a portion of the workpiece in which a predeterminedamount of processing has been effected.

Accordingly, in order to perform processing of an electricallyconductive material with a high processing precision that follows anintended form of a processed workpiece, by the electrolytic processingmethod utilizing the chemical interaction between the reaction speciesand the workpiece, such a control system is needed that does not simplycontrol the contact state (position of tool) between the workpiece andthe tool as is the case of mechanical processing, but also control thechemical interaction between the reaction species, such as OH⁻ ions, andthe atoms of the workpiece.

DISCLOSURE OF INVENTION

The present invention has been made in view of the above situation inthe background art. It is therefore an object of the present inventionto provide an electrolytic processing apparatus and method that cancarry out a uniform processing without suffering from a rapid change inthe processing rate.

It is also an object of the present invention to provide an electrolyticprocessing apparatus and method that can effect processing of aworkpiece, having in the surface an electrically conductive material asa to-be-processed material, with high processing precision and canproduce an intended form of processed workpiece with high accuracy ofform.

In order to achieve the above object, the present invention provides anelectrolytic processing apparatus, comprising: a processing electrodewhich can come close to or in contact with a workpiece; a feedingelectrode for feeding electricity to the workpiece; an ion exchangerdisposed in at least one of the space between the workpiece and theprocessing electrode and the space between the workpiece and the feedingelectrode; a fluid supply section for supplying a fluid to the spacebetween the workpiece and at least one of the processing electrode andthe feeding electrode, in which the ion exchanger is present; and apower source for supplying an electric power between the processingelectrode and the feeding electrode while arbitrarily controlling atleast one of a voltage and an electric current.

In electrolytic processing, the processing rate is high as the electriccurrent supplied between a feeding electrode and a processing electrodeis large (the processing rate is low as the electric current is small).Further, when the voltage supplied between the feeding electrode and theprocessing electrode is raised, the electric current flowing between thefeeding electrode and processing electrode becomes larger and, as aresult, the processing rate becomes higher. Thus, by arbitrarilycontrolling, for example by changing with time, at least one of thevoltage and electric current supplied between a processing electrode anda feeding electrode, it becomes possible to optimize the processing rateaccording to the stage (situation) of processing.

In the above electrolytic processing apparatus, the power source maysupply a constant voltage between the processing electrode and thefeeding electrode, or change at least one of the voltage and theelectric current with time.

The power source may supply constant voltages or constant electriccurrents with changing values sequentially between the processingelectrode and the feeding electrode. Thus, for example, electrolyticprocessing may be carried out by supplying a high electric current or ahigh voltage between the processing electrode and the feeding electrodeuntil the processing comes near to the end point, e.g. until aninterconnect pattern becomes exposed, thereby earning the processingrate, and supplying a low electric current or a low voltage when theprocessing comes near to the endpoint to thereby drop the processingrate, thereby preventing the so-called over-etching.

The power source may supply a constant electric current and a constantvoltage sequentially between the processing electrode and the feedingelectrode. For example, electrolytic processing may be carried out undera controlled constant electric current in the stage of processing whenthere is no change in the processing area of a workpiece, thereby makingthe processing rate constant and facilitating control of the processingrate. When the processing comes near to the end point when theprocessing area rapidly decreases, electrolytic processing may becarried out under a constant voltage so as to facilitate control of theprocessing rate near the end point.

The power source may first supply constant electric currents withchanging values sequentially, and then supply constant voltages withchanging values sequentially between the processing electrode and thefeeding electrode. This makes it possible to first change stepwise theprocessing rate in electrolytic processing as carried out undersequential constant electric currents and then change stepwise theprocessing rate in electrolytic processing as carried out undersequential constant voltages.

Further, the power source may continuously change the voltage or theelectric current with time. This makes it possible to carry outelectrolytic processing at a desired processing rate according to thestage (situation) of processing.

The present invention provides an electrolytic processing method,comprising: providing a processing electrode, a feeding electrode and anion exchanger disposed in at least one of the space between a workpieceand the processing electrode and the space between the workpiece and thefeeding electrode; allowing the processing electrode to be close to orin contact with the workpiece while feeding electricity from the feedingelectrode to the workpiece; supplying a fluid to the space between theworkpiece and at least one of the processing electrode and the feedingelectrode, in which the ion exchanger is present; and supplying anelectric power between the processing electrode and the feedingelectrode while arbitrarily controlling at least one of a voltage and anelectric current.

The present invention also provides electrolytic processing apparatus,comprising: a processing electrode which can come close to or in contactwith a workpiece; a feeding electrode for feeding electricity to theworkpiece; an ion exchanger disposed in at least one of the spacebetween the workpiece and the processing electrode and the space betweenthe workpiece and the feeding electrode; a fluid supply section forsupplying a fluid to the space between the workpiece and at least one ofthe processing electrode and the feeding electrode, in which the ionexchanger is present; and an electricity amount integrator for measuringthe integrated amount of an electricity supplied between the processingelectrode and the feeding electrode.

The present invention also provides electrolytic processing method,comprising: providing a processing electrode, a feeding electrode and anion exchanger disposed in at least one of the space between a workpieceand the processing electrode and the space between the workpiece and thefeeding electrode; allowing the processing electrode to be close to orin contact with the workpiece while feeding electricity from the feedingelectrode to the workpiece; supplying a fluid to the space between theworkpiece and at least one of the processing electrode and the feedingelectrode, in which the ion exchanger is present; and measuring theintegrated amount of an electricity supplied between the processingelectrode and the feeding electrode, and detecting the progress ofprocessing of the workpiece and/or the end point of processing based onthe measured integrated amount of electricity.

The present invention provides another electrolytic processingapparatus, comprising: a holder for detachably holding a workpiece; aprocessing electrode that can come close to or into contact with theworkpiece held by the holder; a feeding electrode for feedingelectricity to the workpiece held by the holder; an ion exchangerdisposed in at least one of the space between the workpiece and theprocessing electrode and the space between the workpiece and the feedingelectrode; a fluid supply section for supplying a fluid between theworkpiece and at least one of the processing electrode and the feedingelectrode, in which the ion exchanger is present; a power source forsupplying an electric power between the processing electrode and thefeeding electrode while controlling at least one of a voltage and anelectric current; a drive section for allowing the workpiece held by theholder and the processing electrode to make a relative movement; and anumerical controller for effecting a numerical control of the drivesection and the power source.

According to this electrolytic processing apparatus, a current valuedata (or a voltage date), which is determined according to apredetermined processing time as well as a processing amountcorresponding to the coordinate difference between the form of aworkpiece before processing and an intended form of the workpiece afterprocessing, or the coordinate difference between the form of a workpieceduring the progress of processing and an intended form of the workpieceafter processing, is inputted to the numerical controller. Based on theinput data, the numerical controller numerically controls the electriccurrent (or voltage) supplied from the power source to between theprocessing electrode and the feeding electrode. The thus controlledelectrolytic processing can produce the intended form of processedworkpiece with high accuracy of form.

The above control is based on the fact that in electrolytic processingas carried out for a predetermined processing time and by processing aworkpiece by a processing electrode disposed opposite to the workpiece,the processing amount depends on the processing rate and therefore onthe value of the electric current (or voltage) supplied between theprocessing electrode and the feeding electrode. In this regard, in suchan electrolytic processing, the processing rate is high as the value ofthe electric current supplied between the processing electrode and thefeeding electrode is large. Further, as a higher voltage is appliedbetween the processing electrode and the feeding electrode, a largercurrent flows between the processing electrode and the feedingelectrode, and consequently the processing rate becomes higher. Theprocessing amount is determined by the product of the processing rateand the processing time.

The apparatus may further comprise an electricity amount monitor formonitoring and measuring the amount of electricity during the progressof processing. As described above, in electrolytic processing as carriedout under a fixed-processing time condition, the processing amountdepends on the value of the electric current (voltage) supplied betweena processing electrode and a feeding electrode. Accordingly, theprocessing amount can be determined by monitoring and measuring theamount of electricity supplied between the processing electrode and thefeeding electrode.

The numerical controller may control the power source according to thecoordinate difference between coordinate data on a measured form of theworkpiece as measured before processing and coordinate data on anintended form of the workpiece after processing. Alternatively, thenumerical controller may control the power source according to thecoordinate difference between coordinate data on a measured form of theworkpiece as measured during the progress of processing and coordinatedate on the intended form of the workpiece.

The numerical controller determines the end point of processing e.g.based on a measured value obtained in the electricity amount monitor. Bythus determining the end point of processing, utilizing the correlationbetween the processing amount and the amount of electricity, bymonitoring and measuring the amount of electricity supplied duringprocessing, it becomes possible to produce an intended form of processedworkpiece with high accuracy-of form.

The present invention provides another electrolytic processing method,comprising: providing a processing electrode, a feeding electrode and anion exchanger disposed in at least one of the space between a workpieceheld by a holder and the processing electrode and the space between theworkpiece and the feeding electrode; allowing the processing electrodeto be close to or in contact with the workpiece held by the holder whilefeeding electricity from the feeding electrode to the workpiece;supplying a fluid to the space between the workpiece and at least one ofthe processing electrode and the feeding electrode, in which the ionexchanger is present; supplying an electric power between the processingelectrode and the feeding electrode while numerically controlling atleast one of a voltage and an electric current by an numericalcontroller; and allowing the workpiece held by the holder and theprocessing electrode to make a relative movement while numericallycontrolling the movement by the numerical controller.

The above and other objects, features, and advantages of the presentinvention will be apparent from the following description when taken inconjunction with the accompanying drawings which illustrates preferredembodiments of the present invention by way of example.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A through 1C are diagrams illustrating, in sequence of processsteps, an example of the formation of copper interconnects;

FIG. 2 is a diagram illustrating the principle of electrolyticprocessing as carried out by using an ion exchanger;

FIGS. 3A through 3D are diagrams illustrating a change in the processingrate in electrolytic processing as carried out under a controlledconstant electric current;

FIG. 4 is a graph showing a change with time in the voltage applied inelectrolytic processing as carried out under a controlled constantelectric current;

FIGS. 5A through 5D are diagrams illustrating a change in the processingrate in electrolytic processing as carried out under a controlledconstant voltage;

FIG. 6 is a graph showing a change with time in the electric current inelectrolytic processing as carried out under a controlled constantvoltage;

FIG. 7 is a longitudinal sectional front view of an electrolyticprocessing apparatus according to an embodiment of the presentinvention;

FIG. 8 is a plan view of the apparatus of FIG. 7;

FIG. 9 is a graph showing an example of voltage and electric currentsupplied between a processing electrode and a feeding electrode;

FIG. 10 is a graph showing another example of voltage and electriccurrent supplied between a processing electrode and a feeding electrode;

FIG. 11 is a graph showing still another example of voltage and electriccurrent supplied between a processing electrode and a feeding electrode;

FIG. 12 is a graph showing still another example of voltage and electriccurrent supplied between a processing electrode and a feeding electrode;

FIG. 13 is a graph showing still another example of voltage and electriccurrent supplied between a processing electrode and a feeding electrode;

FIG. 14 is a graph showing still another example of voltage and electriccurrent supplied between a processing electrode and a feeding electrode;

FIG. 15 is a graph showing still another example of voltage and electriccurrent supplied between a processing electrode and a feeding electrode;

FIG. 16 is a longitudinal sectional front view of an electrolyticprocessing apparatus according to another embodiment of the presentinvention;

FIG. 17 is a plan view of the apparatus of FIG. 16;

FIG. 18 is a longitudinal sectional front view of an electrolyticprocessing apparatus according to still another embodiment of thepresent invention;

FIG. 19 is a plan view of the apparatus of FIG. 18;

FIG. 20 is a longitudinal sectional front view of an electrolyticprocessing apparatus according to still another embodiment of thepresent invention;

FIG. 21 is a plan view of the apparatus of FIG. 20;

FIG. 22 is a longitudinal sectional front view of an electrolyticprocessing apparatus according to still another embodiment of thepresent invention;

FIG. 23 is a diagram illustrating the relationship between thepre-processing form and an intended post-processing form of a workpiece;

FIG. 24 is a block diagram illustrating an example of numerical controlby the electrolytic processing apparatus of FIG. 22;

FIG. 25 is a block diagram illustrating another example of numericalcontrol by the electrolytic processing apparatus of FIG. 22; and

FIG. 26 is a longitudinal sectional front view of an electrolyticprocessing apparatus according to still another embodiment of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will now be describedwith reference to the drawings. Though the below-described embodimentsrefer to application to electrolytic processing apparatuses(electrolytic polishing apparatuses) which use a substrate as aworkpiece to be processed and remove (polish) copper formed on thesurface of the substrate, the present invention is of course applicableto other workpiece, and to other electrolytic processing.

FIGS. 7 and 8 show an electrolytic processing apparatus 36 according toan embodiment of the present invention. This electrolytic processingapparatus 36 includes a substrate holder 46, supported at the free endof a pivot arm 44 that can pivot horizontally, for attracting andholding the substrate W with its front surface facing downward(so-called “face-down” manner), and, positioned beneath the substrateholder 46, a disc-shaped electrode section 48 made of an insulatingmaterial. The electrode section 48 has, embedded therein, fan-shapedprocessing electrodes. 50 and feeding electrodes 52 that are disposedalternately with their surfaces (upper faces) exposed. A film-like ionexchanger 56 is mounted on the upper surface of the electrode section 48so as to cover the surfaces of the processing electrodes 50 and thefeeding electrodes 52.

This embodiment uses, merely as an example of the electrode section 48having the processing electrodes 50 and the feeding electrodes 52, suchone that has a diameter more than twice than that of the substrate W sothat the entire surface of the substrate W may undergo electrolyticprocessing.

The pivot arm 44, which moves up and down via a ball screw 62 by theactuation of a motor 60 for vertical movement, is connected to the upperend of a pivot shaft 66 that rotates by the actuation of a motor 64 forpivoting. The substrate holder 46 is connected to a motor 68 forrotation that is mounted on the free end of the pivot arm 44, and isallowed to rotate by the actuation of the motor 68 for rotation.

The electrode section 48 is connected directly to a hollow motor 70, andis allowed to rotate by the actuation of the hollow motor 70. Athrough-hole 48 a as a pure water supply section for supplying purewater, preferably ultrapure water, is formed in the central portion ofthe electrode section 48. The through-hole 48 a is connected to a purewater supply pipe 72 that vertically extends inside the hollow motor 70.Pure water or ultrapure water is supplied through the through-hole 48 a,and via the ion exchanger 56, is supplied to the entire processingsurface of the substrate W. A plurality of through-holes 48 a, eachconnected to the pure water supply pipe 72, may be provided tofacilitate the processing liquid reaching over the entire processingsurface of the substrate W.

Further, a pure water nozzle 74 as a pure water supply section forsupplying pure water or ultrapure water, extending in the radialdirection of the electrode section 48 and having a plurality of supplyports, is disposed above the electrode section 48. Pure water orultrapure water is thus supplied to the surface of the substrate W fromabove and beneath the substrate W. Pure water herein refers to a waterhaving an electric conductivity of not more than 10 μS/cm, and ultrapurewater refers to a water having an electric conductivity of not more than0.1 μS/cm. Instead of pure water, a liquid having an electricconductivity of not more than 500 μS/cm or any electrolytic solution maybe used. The electric conductivity of the present invention refersherein to that at 25° C., 1 atm. By supplying such a liquid duringprocessing, the instability factors of processing, such as processproducts and dissolved gases, can be removed, and processing can beeffected uniformly with good reproducibility.

According to this embodiment, a plurality of fan-shaped electrode plates76 are disposed in the electrode section 48 in the circumferencedirection, and the cathode and anode of a power source 80 arealternately connected, via a slip ring 78, to the electrode plates 76.The electrode plates 76 connected to the cathode of the power source 80become the processing electrodes 50 and the electrode plates 76connected to the anode of the power source 80 become the feedingelectrodes 52. This applies to processing of e.g. copper, becauseelectrolytic processing of copper proceeds on the cathode side.Depending upon a material to be processed, the cathode side can be afeeding electrode and the anode side can be a processing electrode. Morespecifically, when the material to be processed is copper, molybdenum,iron or the like, electrolytic processing proceeds on the cathode side,and therefore the electrode plates 76 connected to the cathode of thepower source 80 should be the processing electrodes 50 and the electrodeplates 76 connected to the anode should be the feeding electrodes 52. Inthe case of aluminum, silicon or the like, on the other hand,electrolytic processing proceeds on the anode side. Accordingly, theelectrode plates connected to the anode of the power source should bethe processing electrodes and the electrode plates connected to thecathode should be the feeding electrodes.

By thus disposing the processing electrodes 50 and the feedingelectrodes 52 separately and alternately in the circumferentialdirection of the electrode section 48, fixed feeding portions to supplyelectricity to a conductive film (portion to be processed) of thesubstrate is not needed, and processing can be effected to the entiresurface of the substrate. Further, be changing the positive and negativein a pulse manner, an electrolysis product can be dissolved and theflatness of the processed surface can be enhanced by the multiplexrepetition of processing.

With respect to the processing electrode 50 and the feeding electrode52, oxidation or dissolution thereof due to an electrolytic reaction isgenerally a problem. In view of this, it is preferred to use, as a basematerial of the feeding electrode 52, carbon, a noble metal that isrelatively inactive, a conductive oxide or a conductive ceramics, ratherthan a metal or metal compound widely used for electrodes. A noblemetal-based electrode may, for example, be one obtained by plating orcoating platinum or iridium onto a titanium electrode, and thensintering the coated electrode at a high temperature to stabilize andstrengthen the electrode. Ceramics products are generally obtained byheat-treating inorganic raw materials, and ceramics products havingvarious properties are produced from various raw materials includingoxides, carbides and nitrides of metals and nonmetals. Among them thereare ceramics having an electric conductivity. When an electrode isoxidized, the value of the electric resistance generally increases tocause an increase of applied voltage. However, by protecting the surfaceof an electrode with a non-oxidative material such as platinum or with aconductive oxide such as an iridium oxide, the decrease of electricconductivity due to oxidation of the base material of an electrode canbe prevented.

The ion exchanger 56 may be a nonwoven fabric which has ananion-exchange group or a cation-exchange group. A cation exchangerpreferably carries a strongly acidic cation-exchange group (sulfonicacid group) ; however, a cation exchanger carrying a weakly acidiccation-exchange group (carboxyl group) may also be used. Though an anionexchanger preferably carries a strongly basic anion-exchange group(quaternary ammonium group), an anion exchanger carrying a weakly basicanion-exchange group (tertiary or lower amino group) may also be used.

The nonwoven fabric carrying a strongly basic anion-exchange group canbe prepared by, for example, the following method: A polyolefin nonwovenfabric having a fiber diameter of 20-50 μm and a porosity of about 90%is subjected to the so-called radiation graft polymerization, comprisingγ-ray irradiation onto the nonwoven fabric and the subsequent graftpolymerization, thereby introducing graft chains; and the graft chainsthus introduced are then aminated to introduce quaternary ammoniumgroups thereinto. The capacity of the ion-exchange groups introduced canbe determined by the amount of the graft chains introduced. The graftpolymerization may be conducted by the use of a monomer such as acrylicacid, styrene, glicidyl methacrylate, sodium styrenesulfonate orchloromethylstyrene. The amount of the graft chains can be controlled byadjusting the monomer concentration, the reaction temperature and thereaction time. Thus, the degree of grafting, i.e. the ratio of theweight of the nonwoven fabric after graft polymerization to the weightof the nonwoven fabric before graft polymerization, can be made 500% atits maximum. Consequently, the capacity of the ion-exchange groupsintroduced after graft polymerization can be made 5 meq/g at itsmaximum.

The nonwoven fabric carrying a strongly acidic cation-exchange group canbe prepared by the following method: As in the case of the nonwovenfabric carrying a strongly basic anion-exchange group, a polyolefinnonwoven fabric having a fiber diameter of 20-50 μm and a porosity ofabout 90% is subjected to the so-called radiation graft polymerizationcomprising γ-ray irradiation onto the nonwoven fabric and the subsequentgraft polymerization, thereby introducing graft chains; and the graftchains thus introduced are then treated with a heated sulfuric acid tointroduce sulfonic acid groups thereinto. If the graft chains aretreated with a heated phosphoric acid, phosphate groups can beintroduced. The degree of grafting can reach 500% at its maximum, andthe capacity of the ion-exchange groups thus introduced after graftpolymerization can reach 5 meq/g at its maximum.

The base material of the ion exchanger 56 may be a polyolefin such aspolyethylene or polypropylene, or any other organic polymer. Further,besides the form of a nonwoven fabric, the ion-exchanger may be in theform of a woven fabric, a sheet, a porous material, net or short fibers,etc.

When polyethylene or polypropylene is used as the base material, graftpolymerization can be effected by first irradiating radioactive rays(γ-rays or electron beam) onto the base material (pre-irradiation) tothereby generate a radical, and then reacting the radical with amonomer, whereby uniform graft chains with few impurities can beobtained. When an organic polymer other than polyolefin is used as thebase material, on the other hand, radical polymerization can be effectedby impregnating the base material with a monomer and irradiating radioactive rays (γ-rays, electron beam or UV-rays) onto the base material(simultaneous irradiation). Though this method fails to provide uniformgraft chains, it is applicable to a wide variety of base materials.

By using as the ion exchanger 56 a nonwoven fabric having ananion-exchange group or a cation-exchange group, it becomes possiblethat pure water or ultrapure water, or a liquid such as an electrolyticsolution can freely move within the nonwoven fabric and easily arrive atthe active points in the nonwoven fabric having a catalytic activity forwater dissociation, so that many water molecules are dissociated intohydrogen ions and hydroxide ions. Further, by the movement of pure wateror ultrapure water, or a liquid such as an electrolytic solution, thehydroxide ions produced by the water dissociation can be efficientlycarried to the surface of the processing electrodes 50, whereby a highelectric current can be obtained even with a low voltage applied.

When the ion exchanger 56 has only one of anion-exchange group andcation-exchange group, a limitation is imposed on electrolyticallyprocessible materials and, in addition, impurities are likely to formdue to the polarity. In order to solve this problem, the ion exchanger56 may have such a structure wherein anion-exchangers having ananion-exchange group and cation-exchangers having a cation-exchangegroup are concentrically disposed to constitute an integral structure.The anion exchangers and the cation exchangers may be superimposed onthe surface, to be processed, of a substrate. It may also be possible tomake the anion-exchangers and the cation-exchangers each in the shape ofa fan, and dispose them alternately. Alternatively, the ion exchanger 56may carry both of an anion-exchange group and a cation-exchange groupper se. Such an ion exchanger may include an amphoteric ion exchanger inwhich anion-exchange groups and cation-exchange groups are distributedrandomly, a bipolar ion exchanger in which anion-exchange groups andcation-exchange groups are present in layers, and a mosaic ion exchangerin which portions containing anion-exchange groups and portionscontaining cation-exchange groups are present in parallel in thethickness direction. Incidentally, it is of course possible toselectively use, as the ion exchange 56, one having an anion-exchangegroup or one having a cation-exchange group according to the material tobe processed.

The electrolytic processing apparatus 36 is provided with a controller100 that controls the power source 80 so as to allow the power source 80to arbitrarily control at least one of the voltage and the electriccurrent supplied from the power source 80 to between the processingelectrodes 50 and the feeding electrodes 52. The electrolytic processingapparatus 36 is also provided with an electricity amount integrator(coulomb meter) 102 which is connected to a wire extending from thecathode of the power source 80 to detect the current value, determinesthe amount of electricity by the product of the current value and theprocessing time, and integrates the amount of electricity to therebydetermine the total amount of electricity used. An output signal fromthe electricity amount integrator 102 is inputted to the controller 100,and an output signal from the controller 100 is inputted to the powersource 80.

Further, according to this embodiment, wires extending from the cathodeand the anode of the power source 80 are connected to the controller100, and an output signal from the controller 100 is inputted to themotor 60 for vertical movement, whereby the electric current suppliedbetween the processing electrodes 50 and the feeding electrodes 52 canbe controlled at a constant value. When controlling the electric currentsupplied between the processing electrodes 50 and the feeding electrodes52 at a constant value, the current value of the electric current beingsupplied between the processing electrodes 50 and the feeding electrodes52 is measured from the wire extending from the cathode of the powersource 80. When the current value is lowered, for example, the motor 60for vertical movement is driven to lower the substrate holder 46 so asto reduce the distance between the substrate W and the processingelectrodes 50 and feeding electrodes 52, thereby controlling theelectric current at a constant value.

Further, as shown in FIG. 8, a regeneration section 84 for regeneratingthe ion exchanger 56 is provided. The regeneration section 84 comprisesa pivot arm 86 having a structure substantially similar to the pivot arm44 that holds the substrate holder 46 and positioned at the oppositeside to the pivot arm 44 across the electrode section 48, and aregeneration head 88 held by the pivot arm 86 at the free end thereof.In operation, the reverse electric potential to that for processing isgiven to the ion exchanger 56 from the power source 80 (see FIG. 7),thereby promoting dissolution of extraneous matter such as copperadhering to the ion exchanger 56. The regeneration of the ion exchanger56 during processing can thus be effected. The regenerated ion exchanger56 is rinsed by pure water or ultrapure water supplied to the uppersurface of the electrode section 48.

Next, electrolytic processing by the electrolytic processing apparatus36 will be described.

First, a substrate W, e.g. a substrate W as shown in FIG. 1B which hasin its surface a copper film 6 as a conductor film (portion to beprocessed), is attracted and held by the substrate holder 46 of theelectrolytic processing apparatus 36, and the substrate holder 46 ismoved by the pivot arm 44 to a processing position right above theelectrode section 48. The substrate holder 46 is then lowered by theactuation of the motor 60 for vertical movement, so that the substrate Wheld by the substrate holder 46 contacts or gets close to the surface ofthe ion exchanger 56 mounted on the upper surface of the electrodesection 48.

Next, a given voltage or electric current, which is changed with time,is applied from the power source 80 between the processing electrodes 50and the feeding electrodes 52, while the substrate holder 46 and theelectrode section 48 are rotated. At the same time, pure water orultrapure water is supplied, through the through-hole 48 a, from beneaththe electrode section 48 to the upper surface thereof, andsimultaneously, pure water or ultrapure water is supplied, through thepure water nozzle 74, from above the electrode section 48 to the uppersurface thereof, thereby filling pure water or ultrapure water into thespace between the processing and feeding electrodes 50, 52 and thesubstrate W. Thereby, electrolytic processing of the conductor film(copper film 6) formed on the substrate W is effected by hydrogen ionsor hydroxide ions produced in the ion exchanger 56. According to theabove electrolytic processing apparatus 36, a large amount of hydrogenions or hydroxide ions can be produced by allowing pure water orultrapure water to flow within the ion exchanger 56, and the largeamount of such ions can be supplied to the surface of the substrate W,whereby the electrolytic processing can be conducted efficiently.

More specifically, by allowing pure water or ultrapure water to flowwithin the ion exchanger 56, a sufficient amount of water can besupplied to a functional group (sulfonic acid group in the case of anion exchanger carrying a strongly acidic cation-exchange group) therebyto increase the amount of dissociated water molecules, and the processproduct (including a gas) formed by the reaction between the conductorfilm (copper film 6) and hydroxide ions (or OH radicals) can be removedby the flow of water, whereby the processing efficiency can be enhanced.The flow of pure water or ultrapure water is thus necessary, and theflow of water should desirably be constant and uniform. The constancyand uniformity of the flow of water leads to constancy and uniformity inthe supply of ions and the removal of the process product, which in turnleads to constancy and uniformity in the processing.

During the electrolytic processing, at least one of the electric currentand the voltage supplied from the power source 80 to between theprocessing electrodes 50 and the feeding electrodes 52 is changed withtime. Examples thereof are now described with reference to FIGS. 9through 15.

FIG. 9 shows an example of supplying constant voltages with stepwisedecreasing values between the processing electrodes 50 and the feedingelectrodes 52. More specifically, at the initial stage of processing, ahigh constant voltage V₁ is supplied between the processing electrodes50 and the feeding electrodes 52. When the amount of electricity (theshaded area in FIG. 9 and also in the following figures), determined bythe product of the current value and the processing time, reaches apredetermined value (at time t₁), a constant voltage V₂ lower than thevoltage V₁ is supplied between the processing electrodes 50 and thefeeding electrodes 52. When the integrated amount of electricity reachesa predetermined value (at time t₂), a constant voltage V₃ lower than thevoltage V₂ is supplied between the processing electrodes 50 and thefeeding electrodes 52. Further, when the integrated amount ofelectricity reaches a predetermined value (at time t₃), a constantvoltage V₄ lower than the voltage V₃ is supplied between the processingelectrodes 50 and the feeding electrodes 52. The processing isterminated when the integrated amount of electricity reaches apredetermined value (at time t₄), i.e. at the end point of processing.

By thus carrying out electrolytic processing while supplying a highconstant voltage at the initial stage of processing and then supplyinglower constant voltages with stepwise decreasing values as theprocessing reaches the end point to between the processing electrodes 50and the feeding electrodes 52, it becomes possible to earn theprocessing rate at the initial stage of processing and prevent theso-called over-etching.

Though in this example constant voltages with stepwise decreasing valuesare supplied between the processing electrodes 50 and the feedingelectrodes 52, it is also possible to supply constant electric currentswith stepwise decreasing values between the processing electrodes 50 andthe feeding electrodes 52.

FIG. 10 shows an example of first supplying constant electric currentswith changed values sequentially and then supplying constant voltageswith changed values sequentially between the processing electrodes 50and the feeding electrodes 52, in particular first supplying constantelectric currents with stepwise (two steps in FIG. 10) decreasing valuesand then supplying constant voltages with stepwise (two steps in FIG.10) decreasing values between the processing electrodes 50 and thefeeding electrodes 52. More specifically, at the initial stage ofprocessing, a high constant current I₁ is supplied between theprocessing electrodes 50 and the feeding electrodes 52. When the amountof electricity, determined by the product of the current value and theprocessing time, reaches a predetermined value (at time t₅), a constantcurrent I₂ lower than the current I₁ is supplied between the processingelectrodes 50 and the feeding electrodes 52. When the integrated amountof electricity reaches a predetermined value (at time t₆), a constantvoltage V₅ is supplied between the processing electrodes 50 and thefeeding electrodes 52. Further, when the integrated amount ofelectricity reaches a predetermined value (at time t₇), a constantvoltage V₆ lower than the voltage V₅ is supplied between the processingelectrodes 50 and the feeding electrodes 52. The processing isterminated when the integrated amount of electricity reaches apredetermined value (at time t₈), i.e. at the end point of processing.

Such a control of voltage and electric current makes it possible tofirst change stepwise the processing rate in electrolytic processing ascarried out under controlled constant electric currents and then changestepwise the processing rate in electrolytic processing as carried outunder controlled constant voltages. Further, it becomes possible tocarry out electrolytic processing under sequential constant electriccurrents in the stage of processing when there is no change in theprocessing area of a workpiece, thereby sequentially making theprocessing rate constant and facilitating control of the processingrate, and then carry out electrolytic processing under sequentialconstant voltages when the processing comes near to the end point whenthe processing area rapidly decreases, thereby facilitating control ofthe processing rate near the end point.

Though in the example of FIG. 10 constant electric currents with changedvalues are supplied in the plurality of steps and then constant voltageswith changed values are supplied also in the plurality of steps, it ispossible to first carry out processing by supplying a constant electriccurrent for a certain time without changing the value (constant currentprocessing), and then carry out processing by supplying a constantvoltage for a certain time without changing the value (constant voltageprocessing). It is also possible to repeat the constant currentprocessing/constant voltage processing cycle a plurality of times.Further, it is also possible to first supply a constant electric currentwithout changing the value and then supply constant voltages withstepwise changing values in a plurality of steps, or adversely, firstsupply constant electric currents with stepwise changing values in aplurality of steps and then supply a constant voltage without changingthe value.

FIG. 11 shows an example of first supplying a constant voltage betweenthe processing electrodes 50 and the feeding electrodes 52, and thengradually decreasing the voltage supplied between the processingelectrodes 50 and the feeding electrodes 52. More specifically, a highconstant voltage V₇ is first supplied between the processing electrodes50 and the feeding electrodes 52. When the amount of electricity,determined by the product of the current value and the processing time,reaches a predetermined value (at time t₉), the voltage supplied betweenthe processing electrodes 50 and the feeding electrodes 52 is graduallylowered. The processing is terminated when the integrated amount ofelectricity reaches a predetermined value.(at time t₁₀), i.e. at the endpoint of processing.

By thus supplying a constant voltage at the initial stage of processingand then gradually decreasing the voltage with the progress ofprocessing, it becomes possible to earn the processing rate at theinitial stage of processing, and then gradually decrease the processingrate as the processing approaches the end point, thereby preventing theso-called over-etching.

FIG. 12 shows an example of first supplying a constant electric currentbetween the processing electrodes 50 and the feeding electrodes 52, andthen gradually decreasing the electric current supplied between theprocessing electrodes 50 and the feeding electrodes 52. Morespecifically, a high constant current I₃ is first supplied between theprocessing electrodes 50 and the feeding electrodes 52. When the amountof electricity, determined by the product of the current value and theprocessing time, reaches a predetermined value (at time t₁₁), theelectric current supplied between the processing electrodes 50 and thefeeding electrodes 52 is gradually lowered. The processing is terminatedwhen the integrated amount of electricity reaches a predetermined value(at time t₁₂), i.e. at the end point of processing.

Also with this manner of controlling electric current, it is possible toearn the processing rate and prevent over-etching as described above.

FIG. 13 shows an example of first supplying a constant electric currentbetween the processing electrodes 50 and the feeding electrodes 52, thengradually decreasing the electric current supplied between theprocessing electrodes 50 and the feeding electrodes 52, and lastlysupplying a constant low voltage between the processing electrodes 50and the feeding electrodes 52 near the end point of processing. Morespecifically, a high constant current I₄ is first supplied between theprocessing electrodes 50 and the feeding electrodes 52. When the amountof electricity, determined by the product of the current value and theprocessing time, reaches a predetermined value (at time t₁₃), theelectric current supplied between the processing electrodes 50 and thefeeding electrodes 52 is gradually lowered. When the integrated amountof electricity reaches a predetermined amount (at time t₁₄), a constantlow voltage V₈ is supplied between the processing electrodes 50 and thefeeding electrodes 52. The processing is terminated when the integratedamount of electricity reaches a predetermined value (at time t₁₅), i.e.at the end point of processing. This control method can facilitatecontrol of the processing rate near the end point of processing.

FIG. 14 shows an example of gradually and linearly decreasing thevoltage or electric current supplied between the processing electrodes50 and the feeding electrodes 52. More specifically, with respect toelectric current I, the electric current is gradually lowered along theline I=I₀−at (I₀: initial value, a: proportionality constant). Withrespect to voltage V, the voltage is gradually lowered along the lineV=V₀−bt (V₀: initial value, b: proportionality constant). The processingis terminated when the integrated amount reaches a predetermined value(at time t₁₆), i.e. at the end point of processing. This control methodmakes it possible to decrease the processing rate gradually over theentire processing process.

FIG. 15 shows an example of continuously changing the voltage orelectric current supplied between the processing electrodes 50 and thefeeding electrodes 52 along an arbitrary curve. More specifically, withrespect to electric current I, the electric current is changed along anarbitrarily set curve: I=f(t). With respect to voltage V, the voltage ischanged along an arbitrarily set curve: V=f(t). The processing isterminated when the integrated amount of electricity reaches apredetermined value (at time t₁₇), i.e. at the end point of processing.This control method makes it possible to arbitrarily set the processingrate over the entire processing process.

After completion of the electrolytic processing, the power source 80 isdisconnected from the processing electrodes 50 and feeding electrodes52, the rotations of the substrate holder 46 and of the electrodesection 48 are stopped. Thereafter, the substrate holder 46 is raised,and processed substrate W is transferred to next process.

This embodiment shows the case of supplying pure water, preferablyultrapure water, to the space between the electrode section 48 and thesubstrate W. The use of pure water or ultrapure water containing noelectrolyte upon electrolytic processing can prevent extra impuritiessuch as an electrolyte from adhering to and remaining on the surface ofthe substrate W. Further, copper ions or the like dissolved duringelectrolytic processing are immediately caught by the ion exchanger 56through the ion-exchange reaction. This can prevent the dissolved copperions or the like from re-precipitating on the other portions of thesubstrate W, or from being oxidized to become fine particles whichcontaminate the surface of the substrate W.

Ultrapure water has a high resistivity, and therefore an electriccurrent is hard to flow therethrough. A lowering of the electricresistance is made by shortening a distance between the electrode andthe workpiece, or interposing the ion exchanger between the electrodeand the workpiece. Further, an electrolytic solution, when used incombination with electrolytic solutions, can further lower the electricresistance and reduce the power consumption. When electrolyticprocessing is conducted by using an electrolytic solution, the portionof a workpiece that undergoes processing ranges over a slightly widerarea than the area of the processing electrode. In the case of thecombined use of ultrapure water and the ion exchanger, on the otherhand, since almost no electric current flows through ultrapure water,electric processing is effected only within the area of a workpiece thatis equal to the area of the processing electrode and the ion exchanger.

It is possible to use, instead of pure water or ultrapure water, anelectrolytic solution obtained by adding an electrolyte to pure water orultrapure water. The use of such an electrolytic solution can furtherlower the electric resistance and reduce the power consumption. Asolution of a neutral salt such as NaCl or Na₂SO₄, a solution of an acidsuch as HCl or H₂SO₄, or a solution of an alkali such as ammonia, may beused as the electrolytic solution, and these solutions may beselectively used according to the properties of the workpiece. When theelectrolytic solution is used, it is preferred to provide a slightinterspace between the substrate W and the ion exchanger 56 so that theyare not in contact with each other.

Further, it is also possible to use, instead of pure water or ultrapurewater, a liquid obtained by adding a surfactant or the like to purewater or ultrapure water, and having an electric conductivity of notmore than 500 μS/cm, preferably not more than 50 μS/cm, more preferablynot more than 0.1 μS/cm (resistivity of not less than 10 MΩ·cm). Due tothe presence of a surfactant in pure water or ultrapure water, theliquid can form a layer, which functions to inhibit ion migrationevenly, at the interface between the substrate W and the ion exchanger56, thereby moderating concentration of ion exchange (metal dissolution)to enhance the flatness of the processed surface. The surfactantconcentration is desirably not more than 100 ppm.

According to the embodiment, the processing rate can be considerablyenhanced by interposing the ion exchanger 56 between the substrate W andthe processing and feeding electrodes 50, 52. In this regard,electrochemical processing using ultrapure water is effected by achemical interaction between hydroxide ions in ultrapure water and amaterial to be processed. However, the amount of the hydroxide ionsacting as reactant in ultrapure water is as small as 10⁻⁷ mol/L undernormal temperature and pressure conditions, so that the removalprocessing efficiency can decrease due to reactions (such as an oxidefilm-forming reaction) other than the reaction for removal processing.It is therefore necessary to increase hydroxide ions in order to conductremoval processing efficiently. A method for increasing hydroxide ionsis to promote the dissociation reaction of ultrapure water by using acatalytic material, and an ion exchanger can be effectively used as sucha catalytic material. More specifically, the activation energy relatingto water-molecule dissociation reaction is lowered by the interactionbetween functional groups in an ion exchanger and water molecules,whereby the dissociation of water is promoted to thereby enhance theprocessing rate.

Further, according to this embodiment, the ion exchanger 56 is broughtinto contact with or close to the substrate W upon electrolyticprocessing. When the ion exchanger 56 is positioned close to thesubstrate W, though depending on the distance therebetween, the electricresistance is large to some degree and, therefore, a somewhat largevoltage is necessary to provide a requisite electric current density.However, on the other hand, because of the non-contact relation, it iseasy to form flow of pure water or ultrapure water along the surface ofthe substrate W, whereby the reaction product produced on the substratesurface can be efficiently removed. In the case where the ion exchanger56 is brought into contact with the substrate W, the electric resistancebecomes very small and therefore only a small voltage needs to beapplied, whereby the power consumption can be reduced.

If a voltage is raised to increase the current density in order toenhance the processing rate, an electric discharge can occur when theelectric resistance between the electrode and the substrate (workpieceto be processed) is large. The occurrence of electric discharge causespitching on the surface of the workpiece, thus failing to form an evenand flat processed surface. To the contrary, since the electricresistance is very small when the ion exchanger 56 is in contact withthe substrate W, the occurrence of an electric discharge can be avoided.

When electrolytic processing of copper is conducted by using, as the ionexchanger 56, an ion exchanger having a cation-exchange group, theion-exchange group of the ion exchanger (cation exchanger) 56 issaturated with copper after the processing, whereby the processingefficiency of the next processing is lowered. When electrolyticprocessing of copper is conducted by using, as the ion exchanger 56, anion exchanger having an anion-exchange group, fine particles of a copperoxide can be produced and adhere to the surface of the ion exchanger(anion exchanger) 56, which particles can contaminate the surface of anext substrate to be processed.

In operation, in order to obviate such drawbacks, the reverse electricpotential to that for processing is given to the ion exchanger 56 fromthe power source 80, thereby promoting dissolution of extraneous mattersuch as copper adhering to the ion exchanger 56 via regeneration head88. The regeneration of the ion exchanger 56 during processing can thusbe effected. The regenerated ion exchanger 56 is rinsed by pure water orultrapure water supplied to the upper surface of the electrode section48.

FIGS. 16 and 17 show an electrolytic processing apparatus 36 b accordingto another embodiment of the present invention. In this electrolyticprocessing apparatus 36 b, the rotational center O₁ of the electrodesection 48 is distant from the rotational center O₂ of the substrateholder 46 by a distance d; and the electrode section 48 rotates aboutthe rotational center O₁ and the substrate holder 46 rotates about therotational center O₂. Further, the processing electrodes 50 and thefeeding electrodes 52 are connected to the power source 80 via the slipring 78. Further according to this embodiment, the electrode section 48is designed to have a diameter which is larger than the diameter of thesubstrate holder 46 to such a degree that when the electrode section 48rotates about the rotational center O₁ and the substrate holder rotatesabout the rotational center O₂, the electrode section 48 covers theentire surface of the substrate W held by the substrate holder 46.

According to the electrolytic processing apparatus 36 b, electrolyticprocessing of the surface of the substrate W is carried out by rotatingthe substrate W via the substrate holder 46 and, at the same, rotatingthe electrode section 48 by the actuation of the hollow motor 70, whilesupplying pure water or ultrapure water to the upper surface of theelectrode section 48 and applying a given voltage between the processingelectrodes 50 and the feeding electrodes 52.

The electrode section 48 or substrate holder 46 may be made orbitmovement such as scroll movement or reciprocation instead of rotation.

FIGS. 18 and 19 show an electrolytic processing apparatus 36 d accordingto still another embodiment of the present invention. In thiselectrolytic processing apparatus 36 d, the positional relationshipbetween the substrate holder 46 and the electrode section 48 in thepreceding embodiments is reversed, and the substrate W is held with itsfront surface facing upward (so-called “face-up” manner) so thatelectrolytic processing is conducted to the upper surface of thesubstrate. Thus, the substrate holder 46 is disposed beneath theelectrode section 48, holds the substrate W with its front surfacefacing upward, and rotates about its own axis by the actuation of themotor 68 for rotation. On the other hand, the electrode section 48,which has the processing electrodes 50 and the feeding electrodes 52that are covered with the ion exchanger 56 is disposed above thesubstrate holder 46, is held with its front surface downward by thepivot arm 44 at the free end thereof, and rotates about its own axis bythe actuation of the hollow motor 70. Further, wires extending from thepower source 80 pass through a hollow portion formed in the pivot shaft66 and reach the slip ring 78, and further pass through the hollowportion of the hollow motor 70 and reach the processing electrodes 50and the feeding electrodes 52 to apply a voltage therebetween.

Pure water or ultrapure water is supplied from the pure water supplypipe 72, via the through-hole 48 a formed in the central portion of theelectrode section 48, to the front surface (upper surface) of thesubstrate W.

A regeneration section 92 for regenerating the ion exchanger 56 mountedon the electrode section 48 is disposed beside the substrate holder 46.The regeneration section 92 includes a regeneration tank 94 filled withe.g. a dilute acid solution. In operation, the electrode section 48 ismoved by the pivot arm 44 to a position right above the regenerationtank 94, and is then lowered so that at least the ion exchanger 56 ofthe electrode section 48 is immersed in the acid solution in theregeneration tank 94. Thereafter, the reverse electric potential to thatfor processing is given to the electrode plates 76, i.e. by connectingthe processing electrodes 50 to the anode of the power source 80 andconnecting the feeding electrodes 52 to the cathode of the power source80, thereby promoting dissolution of extraneous matter such as copperadhering to the ion exchanger 56 to thereby regenerate the ion exchanger56. The regenerated ion exchanger 56 is rinsed by e.g. ultrapure water.

Further according to this embodiment, the electrode section 48 isdesigned to have a sufficiently larger diameter than that of thesubstrate W held by the substrate holder 46. Electrolytic processing ofthe surface of the substrate W is conducted by lowering the electrodesection 48 so that the ion exchanger 56 contacts or gets close to thesubstrate W held by the substrate holder 46, then rotating the substrateholder 46 and the electrode section 48 and, at the same time, pivotingthe pivot arm 44 to move the electrode section 48 along the uppersurface of the substrate W, while supplying pure water or ultrapurewater to the upper surface of the substrate and applying a given voltagebetween the processing electrodes 50 and the feeding electrodes 52.

FIGS. 20 and 21 show an electrolytic processing apparatus 36e accordingto still another embodiment of the present invention. This electrolyticprocessing apparatus 36 e employs, as the electrode section 48, such onethat has a sufficiently smaller diameter than that of the substrate Wheld by the substrate holder 46 so that the surface of the substrate maynot be entirely covered with the electrode section 48. In thisembodiment, the ion exchanger 56 is of a three-layer structure(lamination) consisting of a pair of strongly acidic cation-exchangefibers 56 a, 56 b and a strongly acidic cation-exchange membrane 56 cinterposed between the fibers 56 a, 56 b. The ion exchanger (laminate)56 has a good water permeability and a high hardness and, in addition,the exposed surface (lower surface) to be opposed to the substrate W hasa good smoothness. Other construction is the same as shown in FIGS. 18and 19. The construction of the ion exchanger 56 may be arranged suchthat the ion-exchange membrane is used for the exposed surface and thelaminate of the ion-exchange fibers is arranged above the exposedion-exchange membrane.

By making the ion exchanger 56 a multi-layer structure consisting oflaminated layers of ion-exchange materials, such as a nonwoven fabric, awoven fabric and a porous membrane, it is possible to increase the totalion exchange capacity of the ion exchanger 56, whereby formation of anoxide, for example, in removal (polishing) processing of copper, can berestrained to thereby avoid the oxide adversely affecting the processingrate. In this regard, when the total ion exchange capacity of an ionexchanger 56 is smaller than the amount of copper ions taken in the ionexchanger 56 during removal processing, the oxide should inevitably beformed on the surface or in the inside of the ion exchanger 56, whichadversely affects the processing rate. Thus, the formation of the oxideis governed by the ion exchange capacity of an ion exchanger, and copperions exceeding the capacity should become the oxide. The formation of anoxide can thus be effectively restrained by using, as the ion exchanger56, a multi-layer ion exchanger composed of laminated layers ofion-exchange materials which has enhanced total ion exchange capacity.

According to the embodiments described hereinabove, uniform processingof e.g. an electrically conductive material can be carried out withoutsuffering from a rapid change in the processing rate even when aninsulating material for forming interconnects becomes exposed on theprocessing surface.

FIG. 22 is a longitudinal sectional front view of an electrolyticprocessing apparatus according to still another embodiment of thepresent invention. This electrolytic processing apparatus includes asubstrate holder 130 for attracting and holding the substrate W with itsfront surface facing upward (so-called “face-up” manner), and anelectrode head 138 having a disc-shaped electrode section 136 made of aninsulating material. The electrode section 136 has, embedded therein,fan-shaped processing electrodes 132 and feeding electrodes 134 that aredisposed alternately with their surfaces (lower faces) exposed. Theelectrode head 138 is positioned above the substrate holder 130. An ionexchanger 140 consisting of laminated layers (lamination) is mounted onthe lower surface of the electrode section 136 so as to cover thesurfaces of the processing electrodes 132 and the feeding electrodes134.

The substrate holder 130 is connected directly to the upper end of amotor shaft 144 of the motor 142 as a first drive section for making therelative movement between the substrate W held by the substrate holder130 and the processing electrodes 132, and is allowed to rotate with thesubstrate W by the actuation of the motor (first drive section) 142 insuch a state that the substrate holder 130 holds the substrate W.

The electrode head 138 is connected downwardly to the free end of apivot arm 146 which can pivot horizontally. The base portion of thepivot arm 146 is connected to the upper end of a hollow pivot shaft 152which moves vertically via a ball screw 150 by the actuation of a motor148 for vertical movement. A motor 154, as a second drive section formaking the relative movement between the substrate W held by thesubstrate holder 130 and the processing electrodes 132, is positionedbeside the pivot arm 152, and allows to move vertically with the pivotarm 152. A timing belt 156 is engaged between the pivot arm 152 and themotor (second drive section) 154 so that the pivot arm 152 and the pivotarm 146 pivots (rotates) integrally by the actuation of the motor(second drive section) 154.

The electrode head 138 is connected directly to a hollow motor 160 as athird drive section for making the relative movement between thesubstrate W held by the substrate holder 130 and the processingelectrodes 132 so as to rotate by the actuation of the hollow motor(third drive section) 160.

In this embodiment, the ion exchanger 140 is of a three-layer structure(lamination) consisting of a pair of strongly acidic cation-exchangefibers 162 a, 162 b and a strongly acidic cation-exchange membrane 162 cinterposed between the fibers 162 a, 162 b. The ion exchanger (laminate)140 has a good water permeability and a high hardness and, in addition,the exposed surface (upper surface) to be opposed to the substrate W hasa good smoothness.

Each of the laminated layers 162 a, 162 b and 162 c of the ion exchanger140 preferably carries a strongly acidic cation-exchange group (sulfonicacid group), however, an ion exchanger carrying a weakly acidiccation-exchange group (carboxyl group), an ion exchanger carrying astrongly basic anion-exchange group (quaternary ammonium group), or anion exchanger carrying a weakly basic anion-exchange group (tertiary orlower amino group) may be used.

By using each of the laminated layers 162 a, 162 b and 162 c of the ionexchanger 140 made of a nonwoven fabric, which liquid can flowstherethough, having an anion-exchange group or a cation-exchange group,it becomes possible that the ion-exchange reaction between ions in theliquid and the ion-exchange group of the ion exchanger can be easilytaken place.

The ion exchanger 140 should preferably have “water permeability andwater-absorbing properties”. Further, it is desirable that at least thematerial to be opposed to the workpiece have a high hardness and goodsurface smoothness. For example, a commercially-available foamedpolyurethane “IC 1000” (manufactured by Rodel, Inc.), generally employedas a pad for CMP, is hard and excellent in wear resistance. By providinga number of through-holes, this product can be used as a material forthe ion exchanger 140. It is possible to provide holes in a resin plate,thereby making the plate water-permeable for use in the ion exchanger140. It is of course desirable that the resin have “water-absorbingproperties”.

A pure water nozzle 170 as a pure water supply section for supplyingliquid, such as pure water or ultrapure water, to between the substrateW held by the substrate-holder 130 and electrode head 138 positionedbelow, is disposed above the electrode holder 130. Pure water orultrapure water is thus supplied to the ion exchanger 140.

The electrolytic processing apparatus is provided with a numericalcontroller 172 for effecting numerical control of the drive sections,i.e. the motor (first drive section) 142, the motor (second drivesection) 154 and the motor (third drive section) 160, which allow thesubstrate W held by the substrate holder 130 and the processingelectrodes 132, facing each other, to make a relative movement. Themotors (drive sections) 142, 154 and 160 are thus numericallycontrollable servomotors, and their rotation angles and rotationalspeeds are numerically controlled by an output signal from the numericalcontroller 172. According to this embodiment, the motor 148 for verticalmovement also is a servomotor, and is numerically controlled by anoutput signal from the numeral controller 172.

The electrolytic processing apparatus is also provided with anelectricity amount monitor 174 which is connected to a wire extendingfrom a power source 168 to monitor and measure the amount of electricityduring the progress of processing. According to this embodiment, theelectricity monitor 174 comprises an electricity amount integrator(coulomb meter) which determines the amount of electricity by theproduct of the current value of the electric current, supplied from thepower source 168, and the processing time, and integrates the amount ofelectricity to thereby determine the total amount of electricity used.An output signal from the electricity monitor 174 is inputted to thenumerical controller 172.

According to this embodiment, during electrolytic processing carried outfor a predetermined time, the numeral controller 172 numericallycontrols: the rotational speed of the substrate W, held by the substrateholder 130, via the motor (first drive section) 142; the speed of thehorizontal movement of the electrode head 138, by pivoting of the pivotarm 146, via the motor (second drive section) 154; the rotational speedof the electrode head 138 via the motor (third drive section) 160; andthe relative movement speed between the substrate W and the electrodehead 138. Further, in the electrolytic processing, an electric power issupplied between the processing electrodes 132 and the feedingelectrodes 134 while controlling at least one of the electric currentand the voltage.

An example of the numerical control will now be described with referenceto FIGS. 23 and 24. First, as shown in FIG. 23, the form of a workpiecebefore processing is measured. Specifically, various coordinate pointsof the pre-processing form are measured in a X-Y-Z coordinate system (inwhich the Z axis is orthogonal to the X-Y plane as a datum plane). Themeasured pre-processing form data is inputted to the numericalcontroller 172. Further, with respect to a coordinate point (x, y, Z₁)of the pre-processing form, the corresponding coordinate point (x, y,Z₂) of an intended post-processing form is also inputted as intendedform data to the numerical controller 172. In addition, unit processingform data e.g. on voltage dependence of processing rate, i.e. therelationship between processing rate and voltage applied between theprocessing electrodes 132 and the feeding electrodes 134, and data onthe relative speed between the processing electrodes 132 and theworkpiece W are inputted to the numerical controller 172 in advance orat an arbitrary time.

When electrolytic processing is carried out for a controlled fixedprocessing time under control of the relative movement speed between theprocessing electrodes 132 and the workpiece W, the processing amountdepends on the processing rate, and therefore on the voltage (or currentvalue) applied between the processing electrodes 132 and the feedingelectrodes 134. Accordingly, in the case of fixing the processing time,i.e. a period of time during which the workpiece W and the processingelectrodes 132 are in face-to-face positions and the electrolyticprocessing phenomenon occurs (residence time), numerical control only ofthe voltage (or current value) applied between the processing electrodes132 and the feeding electrodes 134 can produce an intended form ofprocessed workpiece with high accuracy of form.

Thus, according to this embodiment, a processing amount Z₁-Z₂ in the Zdirection is determined at each coordinate point based on the datainputted in the numerical controller 172. Based on the processing amountZ₁-Z₂ the voltage (or current value) to be applied between theprocessing electrodes 132 and the feeding electrodes 134 is determinedfor each coordinate point, and the signal is inputted to the powersource 168 so as to numerically control the voltage (or current value)applied from the power source 168 to between the processing electrodes132 and the feeding electrodes 134.

Next, electrolytic processing by this electrolytic processing apparatuswill be described.

First, a substrate W. e.g. a substrate W as shown in FIG. 1B which hasin its surface a copper film 6 as a conductor film (portion to beprocessed), is attracted and held by the substrate holder 130, and theelectrode head 138 is moved by the pivot arm 146 to a processingposition right above the substrate W held by the substrate holder 130.The electrode head 138 is then lowered by the actuation of the motor 148for vertical movement; so that the ion exchanger 140 mounted on thelower surface of the electrode section 136 of the electrode head 138contacts or gets close to the upper surface of the substrate W held bythe substrate holder 130.

Next, an electric power is applied from the power source 168 to betweenthe processing electrodes 132 and the feeding electrodes 134, while atleast one of the voltage and the current value being controlled, and thesubstrate holder 130 and the electrode head 130 are rotated. Further,the pivot arm 146 is pivoted to move the electrode head 138horizontally. At the same time, pure water or ultrapure water issupplied, from above the electrode substrate holder 130 to between thesubstrate W and the electrode head 138, thereby filling pure water orultrapure water into the space between the processing and feedingelectrodes 132, 134 and the substrate W. Thereby, electrolyticprocessing of the conductor film (copper film 6) formed on the substrateW is effected by hydrogen ions or hydroxide ions produced in the ionexchanger 140.

More specifically, pure water or ultrapure water is dissociated into OH⁻ions and H⁺ ions with the aid of a catalytic reaction in the ionexchanger 140. The OH⁻ ions transfer the electric charges in thevicinity of the copper film 6 and become OH radicals. The OH radicalsare reacted with the copper film 6 of the substrate W to thereby effectremoval (polishing) processing of the film. In order to shut off H₂ gasgenerated at the feeding electrodes 134, a gas-impermeable ion membranemay be used as the strongly acidic cation-exchange membrane 162 c. TheH₂ gas is thus shut off, and is discharged out by the flow of pure wateror ultrapure water produced by the rotation of the electrode section136.

In advance of or during processing, the pre-processing form data orin-processing form data during processing, the unit processing formdata, and the data of the relative movement of the processing electrodesand the workpiece are inputted to the numerical controller 172.Electrolytic processing is carried out for a predetermined time whilenumerically controlling: the rotational speed of the substrate W, heldby the substrate holder 130, via the motor (first drive section) 142;the speed of the horizontal movement of the electrode head 138, bypivoting of the pivot arm 146, via the motor (second drive section) 154,the rotational speed of the electrode head 138 via the motor (thirddrive section) 160; and the relative movement speed between theworkpiece W and the electrode head 138. In the electrolytic processing,an electric power is supplied between the processing electrodes 132 andthe feeding electrodes 134 while controlling at least one of theelectric current and the voltage. The electrolytic processing canproduce an intended form of processed workpiece with high accuracy ofform.

During the electrolytic processing, the amount of electricity suppliedfrom the power source 168 to between the processing electrodes 132 andthe feeding electrodes 134 is monitored and measured by the electricityamount monitor 174. Thus, the amount of electricity is determined by theproduct of the current value of the electric current supplied from thepower source 168 and the processing time. The amount of electricity isintegrated to determine the total amount of electricity used. Inelectrolytic processing as carried out for a fixed processing time, theprocessing amount depends on the value of the electric current (orvoltage) supplied between the processing electrodes 132 and the feedingelectrodes 134. Accordingly, the processing amount can be determined bymonitoring and measuring the amount of electricity. The processing isterminated when the integrated amount of electricity reaches apredetermined value, i.e. at the end point of processing. By thusdetermining the end point of processing, utilizing the correlationbetween the processing amount and the amount of electricity, bymonitoring and measuring the amount of electricity supplied during theprocessing, it becomes possible to produce an intended form of processedworkpiece with high accuracy of form.

After completion of the electrolytic processing, the power source 168 isdisconnected, the rotation of the substrate holder 130 and the electrodehead 138 are stopped, and pivoting of the pivot arm 146 is stopped.Thereafter, the electrode head 138 is raised, and processed substrate Wheld by the substrate holder 130 is transferred to next process.

According to this embodiment, a relative step operation can be carriedout optionally. Thus, the motor 142 for rotating the substrate holder130 for holding the substrate (workpiece) W is mounted on the uppersurface of a X-Y table (first drive section) 178 having an X stage 176 athat moves in the X direction by the actuation of a motor 175 a, and a Ystage 176 b that moves in the Y direction by the actuation of a motor175 b. The motors 175 a, 175 b are numerically controllable servomotors,and their rotation angles and rotational speeds are numericallycontrolled by an output signal from the numerical controller 172.

An example of the numerical control for carrying out the step operationwill now be described with reference to FIG. 25 First, as illustrated inFIG. 23, the form of the workpiece W before processing is measured bymeasuring various coordinate points of the pre-processing form in aX-Y-Z coordinate system (in which the Z axis is orthogonal to the X-Yplane as a datum plane). The measured pre-processing form data isinputted to the numerical controller 172. Further, with respect to acoordinate point (x, y, Z₁) of the pre-processing form, thecorresponding coordinate point (x. y, Z₂) of an intended post-processingform is also inputted to the numerical controller 172. In addition, unitprocessing form data, e.g. on voltage dependence of processing rate, anddata on a period of time during which the workpiece faces the processingelectrodes are inputted to the numerical controller 172 in advance or atan arbitrary time.

According to this embodiment, a processing amount Z₁-Z₂ in the Zdirection is determined at each coordinate point based on the datainputted in the numerical controller 172. Based on the processing amountZ₁-Z₂, the voltage (or current value) to be applied between theprocessing electrodes 132 and the feeding electrodes 134 is determinedfor each coordinate point, and the signal is inputted to the powersource 168 so as to numerically control the voltage (or current value)applied from the power source 168 to between the processing electrodes132 and the feeding electrodes 134 while supplying an electric powertherebetween.

According to this embodiment, e.g. a substrate W as shown in FIG. 1B,having copper film 6 as a conductive film (to-be-processed portion) inthe surface, is attracted and held by the substrate holder 130. The ionexchanger 140 mounted on the processing electrodes 132 is brought closeto or into contact with the surface of the substrate W. Electrolyticprocessing is then carried out by supplying an electric power betweenthe processing electrodes 132 and the feeding electrodes 134 whilecontrolling the voltage (or electric current) by the numericalcontroller 172 and rotating the electrode head 138.

During the electrolytic processing, a step operation, which makes arepetition of movement and stop of the substrate W in the X or Ydirection, is carried out. For this operation, as described above, thepre-processing form data, the intended form data, the unit processingform data and the workpiece-electrodes face-to-face time data areinputted to the numerical controller 172 in advance, thereby numericallycontrolling: the rotation of the electrode head 138 via the motor 160;the movement of the X-Y table (fourth drive section) 178 via the motors175 a, 175 b; and the voltage (or electric current) applied between theprocessing electrodes 132 and the feeding electrodes 134 via the powersource 168. Thus, the processing time, i.e. the time during which theelectrode head 138 faces a given portion of the substrate to carry outelectrolytic processing of the portion, is controlled by respectivelycontrolling the motor 160 and the motors 175 a, 175 b of the X-Y table178, thereby carrying out the electrolytic processing for apredetermined time. During the electrolytic processing, the voltage (orelectric current) applied between the processing electrodes 132 and thefeeding electrodes 134 is numerically controlled. Such an electricprocessing can produce the intended form of processed substrate withhigh accuracy of form.

The “relative step operation” herein refers to a operation which allowseither one or both of the X-Y table and the processing electrodes 132 tomove or make a relative movement so that the processing electrodes 132makes a repetition of a certain-distance movement and stop over thesubstrate W.

FIG. 26 shows an -electrolytic processing apparatus according to stillanother embodiment of the present invention. The electrolytic processingapparatus has a ring-shaped contact holding plate 180 at the peripheryof the upper surface of the substrate holder 130. A plurality ofinwardly-protruding contacts 182 as feeding electrodes are mounted at agiven pitch to the contact holding plate 180. Further, the electrodehead 138 is provided with a processing electrode. 184 instead of theelectrode section 136 used in the embodiment of FIG. 22. The processingelectrode 184 is connected to the cathode of the power source 168 via aslip ring 186, and the contacts (feeding electrodes) 182 are connectedto the anode of the power source 168. The other construction is the sameas the apparatus shown in FIG. 22.

According to this embodiment, when a substrate W is held by thesubstrate holder 130, the contacts (feeding electrodes) 182 contact thecopper layer 6 as a to-be-processed material, deposited on the surfaceof the substrate W as shown in FIG. 1B. Electrolytic processing can becarried in the same manner as in the preceding embodiment. Thus, theelectrode head 138 is lowered, and an electric power is applied from thepower source 168 to between the processing electrode 184 and thecontacts (feeding electrodes) 182 while numerically controlling at leastone of the voltage or the electric current. At the same time, thesubstrate holder 130 and the electrode head 138 are rotated, while thepivot arm 146 is pivoted to move the electrode head 138 horizontally, orthe electrode head 138 is rotated, while the substrate W held by thesubstrate holder 130 is allowed to make a repetition of a movement andstop, i.e. a step movement, via the X-Y table 178. At the same time,pure water or ultrapure water is supplied from the pure water nozzle 170to between the substrate W and the processing electrode 184.Electrolytic processing of the conductive film (copper film 6) of thesubstrate W is thus effected.

In advance of the electrolytic processing, as with the processingembodiment, the pre-processing form data, the intended form data, theunit processing form data, etc. are inputted to the numerical controller172 so as to control the processing time, i.e. a period of time duringwhich the substrate Wand the processing electrode 184 are inface-to-face positions, so that the electrolytic processing phenomenonoccurs (residence time), at a predetermined time and, at the same,numerically control the voltage (or electric current) applied betweenthe processing electrode 184 and the contacts (feeding electrodes) 182.The electrolytic processing carried out under such a control can producean intended form of processed substrate W with high accuracy of form.

The control of the voltage applied between the processing electrode 184and the contacts (feeding electrodes) 182 makes use of the fact that asthe voltage is increased, the electric current flowing between theprocessing electrode and the feeding electrode becomes larger and theprocessing rate becomes higher in proportion thereto, and vice versa.

The measurement of the form of a workpiece may be carried out not onlybefore processing but also at any time during processing any number oftimes. In this connection, there is a case where the actual processingtime becomes different from a predetermined processing time. Thedifference can lead to a lowered accuracy of form of the resultingprocessed workpiece. Such a lowering of accuracy may be eliminated orreduced by effecting in-processing measurement of the workpiece as manytimes as possible. Thus, an increased number of in-processingmeasurements can generally enhance the processing precision.

According to the embodiments described hereinabove, an electric currentvalue data (or a voltage data), which is determined according to apredetermined processing time as well as a processing amountcorresponding to the coordinate difference between the form of aworkpiece before processing and an intended form the workpiece afterprocessing or the coordinate difference between the form of a workpieceduring the progress of processing and an intended form of the workpieceafter processing, is inputted to the numerical controller Based on theinputted data, the numerical controller numerically controls theelectric current (or voltage) supplied from a power source to between aprocessing electrode and a feeding electrode. The thus controlledelectrolytic processing can produce an intended form of processedworkpiece with high accuracy of form.

Although certain preferred embodiments of the present invention havebeen shown and described in detail, it should be understood that variouschanges and modifications may be made therein without departing from thescope of the appended claims.

The present application is based on the International ApplicationPCT/JP02/01545, filed Feb. 21, 2002, the entire disclosure of which ishereby incorporated by reference.

Industrial Applicability

This invention relates to an electrolytic processing apparatus andmethod useful for processing a conductive material present in thesurface of a substrate, especially a semiconductor wafer, or forremoving impurities adhering to the surface of a substrate.

1. An electrolytic processing apparatus, comprising: a processingelectrode which can come close to or in contact with a workpiece; afeeding electrode for feeding electricity to the workpiece; an ionexchanger disposed in at least one of the space between the workpieceand the processing electrode and the space between the workpiece and thefeeding electrode; a fluid supply section for supplying a fluid to thespace between the workpiece and at least one of the processing electrodeand the feeding electrode, in which the ion exchanger is present; and apower source for supplying an electric power between the processingelectrode and the feeding electrode while arbitrarily controlling atleast one of a voltage and an electric current.
 2. The electrolyticprocessing apparatus according to claim 1, wherein the power sourcesupplies a constant voltage between the processing electrode and thefeeding electrode.
 3. The electrolytic processing apparatus according toclaim 1, wherein the power source supplies an electric power between theprocessing electrode and the feeding electrode, while changing at lastone of the voltage and the electric current with time.
 4. Theelectrolytic processing apparatus according to claim 1, wherein thepower source supplies constant voltages or constant electric currentswith changing values sequentially between the processing electrode andthe feeding electrode.
 5. The electrolytic processing apparatusaccording to claim 1, wherein the power source supplies a constantelectric current and a constant voltage sequentially between theprocessing electrode and the feeding electrode.
 6. The electrolyticprocessing apparatus according to claim 1, wherein the power sourcefirst supplies constant electric currents with changing valuessequentially, and then supplies constant voltages with changing valuessequentially between the processing electrode and the feeding electrode.7. An electrolytic processing method, comprising: providing a processingelectrode, a feeding electrode and an ion exchanger disposed in at leastone of the space between a workpiece and the processing electrode andthe space between the workpiece and the feeding electrode; allowing theprocessing electrode to be close to or in contact with the workpiecewhile feeding electricity from the feeding electrode to the workpiece;supplying a fluid to the space between the workpiece and at least one ofthe processing electrode and the feeding electrode, in which the ionexchanger is present; and supplying an electric power between theprocessing electrode and the feeding electrode while arbitrarilycontrolling at least one of a voltage and an electric current.
 8. Theelectrolytic processing method according to claim 7, wherein a constantvoltage is supplied between the processing electrode and the feedingelectrode.
 9. The electrolytic processing method according to claim 7,wherein the power source applies an electric power between theprocessing electrode and the feeding electrode, while at least one ofthe voltage and the electric current changing with time.
 10. Theelectrolytic processing method according to claim 7, wherein the powersource applies constant voltages or constant electric currents withchanging values sequentially between the processing electrode and thefeeding electrode.
 11. The electrolytic processing method according toclaim 7, wherein the power source applies a constant current and aconstant voltage sequentially between the processing electrode and thefeeding electrode.
 12. An electrolytic processing apparatus, comprising:a processing electrode which can come close to or in contact with aworkpiece; a feeding electrode for feeding electricity to the workpiece;an ion exchanger disposed in at least one of the space between theworkpiece and the processing electrode and the space between theworkpiece and the feeding electrode; a fluid supply section forsupplying a fluid to the space between the workpiece and at least one ofthe processing electrode and the feeding electrode, in which the ionexchanger is present; and an electricity amount integrator for measuringthe integrated amount of an electricity supplied between the processingelectrode and the feeding electrode.
 13. An electrolytic processingmethod, comprising: providing a processing electrode, a feedingelectrode and an ion exchanger disposed in at least one of the spacebetween a workpiece and the processing electrode and the space betweenthe workpiece and the feeding electrode; allowing the processingelectrode to be close to or in contact with the workpiece while feedingelectricity from the feeding electrode to the workpiece; supplying afluid to the space between the workpiece and at least one of theprocessing electrode and the feeding electrode, in which the ionexchanger is present; and measuring the integrated amount of anelectricity supplied between the processing electrode and the feedingelectrode, and detecting the progress of processing of the workpieceand/or the end point of processing based on the measured integratedamount of electricity.
 14. An electrolytic processing apparatus,comprising: a holder for detachably holding a workpiece; a processingelectrode that can come close to or into contact with the workpiece heldby the holder; a feeding electrode for feeding electricity to theworkpiece held by the holder; an ion exchanger disposed in at least oneof the space between the workpiece and the processing electrode and thespace between the workpiece and the feeding electrode; a fluid supplysection for supplying a fluid between the workpiece and at least one ofthe processing electrode and the feeding electrode, in which the ionexchanger is present; a power source for supplying an electric powerbetween the processing electrode and the feeding electrode whilecontrolling at least one of a voltage and an electric current; a drivesection for allowing the workpiece held by the holder and the processingelectrode to make a relative movement; and a numerical controller foreffecting a numerical control of the drive section and the power source.15. The electrolytic processing apparatus according to claim 14, furthercomprising an electricity amount monitor for monitoring and measuringthe amount of electricity during the progress of processing.
 16. Theelectrolytic processing apparatus according to claim 14, wherein thenumerical controller controls the power source according to thecoordinate difference between coordinate data on a measured form of theworkpiece as measured before processing and coordinate data on anintended form of the workpiece after processing.
 17. The electrolyticprocessing apparatus according to claim 14, wherein the numericalcontroller controls the power source according to the coordinatedifference between coordinate data on a measured form of the workpieceas measured during the progress of processing and coordinate data on anintended form of the workpiece after processing.
 18. The electrolyticprocessing apparatus according to claim 15, wherein the numericalcontroller determines the end point of processing based on a measuredvalue obtained in the electricity amount monitor.
 19. An electrolyticprocessing method, comprising: providing a processing electrode, afeeding electrode and an ion exchanger disposed in at least one of thespace between a workpiece held by a holder and the processing electrodeand the space between the workpiece and the feeding electrode; allowingthe processing electrode to be close to or in contact with the workpieceheld by the holder while feeding electricity from the feeding electrodeto the workpiece; supplying a fluid to the space between the workpieceand at least one of the processing electrode and the feeding electrode,in which the ion exchanger is present; supplying an electric powerbetween the processing electrode and the feeding electrode whilenumerically controlling at least one of a voltage and an electriccurrent by an numerical controller; and allowing the workpiece held bythe holder and the processing electrode to make a relative movementwhile numerically controlling the movement by the numerical controller.20. The electrolytic processing method according to claim 19,comprising: measuring the form of the workpiece before processing;inputting coordinate data on the measured form and on an intended formafter processing of the workpiece to the numerical controller; andsupplying an electric power between the processing electrode and thefeeding electrode while controlling at least one of a voltage and anelectric current according to the coordinate difference between themeasured form and the intended form.
 21. The electrolytic processingmethod according to claim 19, comprising: measuring the form of theworkpiece during the progress of processing; inputting coordinate dataon the measured form and on an intended form after processing of theworkpiece to the numerical controller; and supplying an electric currentbetween the processing electrode and the feeding electrode whilecontrolling at least one of a voltage and an electric current accordingto the coordinate difference between the measured form and the intendedform.